Diesel engine having controllable auxiliary burner means to supplement exhaust gas fed to turbocharger



Dec. 9, 1952 F. NETTEL DIESEL ENGINE HAVING CONTROLLABLE AUXILIARY BURNER MEANS T0 SUPPLEMENT EXHAUST GAS FED TO TURBOCHARGER Filed April 6, 1946 14} 1 ENGINE s 25 conpnsssso GAS PREJl/RA CHARGER TORQUE Elb J CHARGER FY 1 20b Y 9' R1 22b .rcdz/u'ckj A INVENTOR.

BY W

Patented Dec. 9, 1952 UNITED STATES PATENT OFFICE DIESEL ENGINE HAVING CONTROLLABLE AUXILIARY BURNER MEANS T SUPPLE- MENT EXHAUST GAS FED TO TURBO- CHARGER 7 Claims.

This invention relates to reciprocating internal combustion engines. More particularly, the invention pertains to mea s for supercharging reciprocating internal combustion engines, e. g. those running on the Otto or diesel cycles.

Conventional engines of the character described inherently furnish an approximately constant torque in the useful speed ranges. However, many uses of these engines require an approximately constant output over a considerable speed range. Examples of such uses are passenger automobiles, trucks, buses, locomotives and cranes. At the present time the desired torquespeed relationship (high torque at low drive shaft speed and low torque at high drive shaft speeds) is obtained by interposing a variable speed change device between the engine and the drive shaft, thus enabling the engine, for example, to run at a high speed and deliver a high output, when desired, while the drive shaft turns at a lower speed. Many different types of such speed change devices are used, automobile transmissions, hydraulic pump-turbine sets and electric generatormotor sets being exemplitive. Said devices are expensive, bulky and heavy.

It is an object of my invention to provide an engine of the character described which is able to deliver greater crankshaft torques at low speeds than at high speeds.

It'is a further object of my invention to provide an engine of the character described which is able to deliver an approximately constant power output within a wide speed range without the use of speed change devices.

It is another object of my invention to provide an engine of the character described which Will accomplish the foregoing desirable results with- :out an increase in the size, weight and cost of the engine and its auxiliaries large enough to off- :set the elimination of the aforementioned speed change devices.

In general I accomplish the above objects of my invention by employing a supercharger. It is known standard practice to supercharge reciprocating internal combustion engines by means of centrifugal or axial flow blowers driven by exhaust gas turbines. The most successful of these superchargers are those which are mechanically independent of the engine shafts. However, these .superchargersQwhich are mainly used with fourcycle engines, primarily are designed to increase torque at high speeds and loads, obviously a desirable feature, and their degree of supercharging decreases as the load and speed of the engine drop.

It is, therefore, another object of my invention to provide a supercharger and system of engine operation differing from the conventional in that the pressure furnished by the supercharger remains constant, or even increases as the engine speed drops.

It is an additional object of my invention to provide a supercharger and system of engine operation in which the degree of supercharging can be varied so as to enable an engine to furnish substantial overloads at any speed.

It is a further specific object of my invention to provide a supercharger and system of engine operation which facilitates starting of highly supercharged four-cycle engines.

Still another object of my invention is to employ my improved supercharger and system of engine operation to enable two-cycle engines with mechanically independent supercharger sets to be started, and to be operated at low loads and speeds, including idling.

Yet another object of my invention is to provide in conjunction with improved superchargers of the character described control devices for the blowers and gas turbines which enable the superchargers to satisfy the charging and scavenging requirements of the engines under all conditions of engine operation.

Other objects of my invention will in part be obvious and in part hereinafter pointed out.

My invention accordingly consists in the features of construction, arrangements of elements, and. combinations of parts illustrated in the drawing and described in detail hereinafter, andthe scope of which will be apparent from the appended claims. 7

In the accompanying drawing, in which are shown various possible embodiments of my invention,

Fig. 1 is a schematic view of a diesel engine with a supercharger set embodying my invention;

Fig. 2 is a similar view of a modified form of my invention;

Fig. 3 is a schematic view of a modified form of supercharger set according to my invention; and

Fig. 4 is a view similar to Fig. 1 showing an other modified form of my invention.

In known supercharging systems the degree of supercharging adjusts r balances itself automatically in such a manner that the power extracted by the turbine from the energy of the exhaust gases just balances the power required by the blower. This determines a certain speedtorque characteristic for the enginewhich up to now could not bev'aried, except .by bypassing exhaust gases to the atmosphere and thereby reducing the supercharging.

However, as already indicated, it is often desirable to either maintain the degree of supercharging with falling engine loador'speed, or even to increase it, since increasing supercharging means higher mean effective pressures and consequently higher torque. Obviously, to achieve this the gas turbine must be able to supply either constant power or its power must even rise.

With dropping engine speed the energy derivable by the gas turbine from the exhaust gases also drops. However, pursuant to my invention, I boost the energy 'content of the gases supplied" to the turbine, preferably accomplishing this result by burning fuel outside of the engine and feeding the product of this combustion to the driving side of the turbo-blower set. Although the pressure differential. necessary for effectivescavenging and charging of the engine can, of course, be supplied by meansindependent of said set, it is desirable to derive the corresponding power from the output side of the set itself, e. g.'the turbine driven shaft. Highly satisfactory results are obtainable and the mechanical elements kept few andv simple when the requisite additional turbine power is secured by branching off a portion of the air issuing from the blower, burning fuel in said branched off air and then re -expanding the same in the turbine which drives the blower. The work produced by the branched off highly heated air is in excess of thatjneeded for compressing the same quantity of air in the blower, thus making more power available in the turbine. This power can, according. to my. invention, be used indifferent ways (a) for producing overload in the engine by compressing the charge higher, or (b) at, partial engine loads, for maintaining the degree of supercharge, or (c) with falling engine speed at constant fuel input to the engine, forincreasing the charging pressure and consequently increasing the engine torque to maintain substantially constant the output of the engine or to approximate such condition.

Referring now more particularly to Fig. 1 of the drawing I 0 denotes an engine having an intake manifold I I and an intake pipe I Ia for scavenging and charging air, an exhaust gas manifold I2 and an exhaust gas pipe IZa. A fuel inlet line I3 to theengine is provided with a control valve like. The .intakepipe IIia is connected to the outlet of a blower I9 of a blower supercharging set S. At a point Ilb in the pipe Ha, a bypass con duit I 4 is branched off and connected to inlet nozzles of gas turbine 2| of the supercharger set S. Flow of air through the conduit I4 is controlled by aflap valve I6 at thebranch point. Interposedin the conduit I4 is anauxiliary combustion chamberIS to which fuel is admitted by a pipe I 7 having a control valve I8. The exhaust pipe I2a also leads to the inlet nozzles of the turbine 2|. and 22 denote the air intake from the atmosphere to the blower I9, and the exhaust gas discharge to the atmosphere from the turbine 2 I, respectively. As can be seen from the drawing the blower and turbine are mounted on a common shaft.

Normally, as is well known in the art, the exhaust gases from the engine drive the turbine 21 and enable the blower I9 to supply compressed air to the engine through the intake manifold I I. The speed of the supercharger set rises and falls with. the engine load and/or speed, causing the charging pressurepto varyjaccordingly. Under such operating conditions the valves I6 and I8 may be fully closed or preferably slightly opened, sufficiently only to admit enough air and fuel to the combustion chamber I5 to keep an idling flame burning therein.

If now an. overload at constant engine speed is required, this may be obtained by admitting more fuel to the engine. There is, however, but a comparatively small margin left for such load increase due to the fact that the cylinder charge soon becomes insufficient to burn more fuel and incomplete combustion results. Pursuant to my invention, I increase the air charge at the same time that more fuelis admitted, achieving this result by raising, the supercharging pressure. This higher pressure is secured by opening of valves I6 and I 8' and b'y burning more fuel in the combustion chamber I5. Thus I obtain a substantial overload with good combustion.

At first glance this may appear to be an erroneous method for increasing thecharging pressure since, instead of increasing pressure, this causes a pressure drop in. the intake pipe Ila. However, such apparently erroneous operation is, as will presently be seen, quite correct. When the foregoing procedure is started, the supercharger set will continue to run for a while at about the same speed, since the engine begins to receive more fuel. But the larger quantity of air branched off through fiap valve I6 is heated to a very high temperature (as high as is permissible for the turbine blades) in combustion chamber I5 and expands in the turbine 2| producing substantially more work than is needed to compress the same air quantity in the blower I9. This extra power now adds to the power produced in the turbine 2! by the engine exhaust andenables the supercharger set to speed up, supplying air of higher pressure both to the engine and to'the turbine via the conduit I4. Anew equilibrium speed for the supercharger will establish itself. when the increased turbine power again equals the power required for the blower. Since the engine air charge is increased, the fuel supply to the engine also can be increased, enabling the engine to furnish the required overload.

Obviously this mode of operation is not restricted to overload but also can be adopted for partial loads. This .means that the supercharging pressure at partial loads can be maintained at any desired. value which may be desired in the circumstances.

If desired, I may subdivide the turbine nozzles to provide separate sets of. nozzles for the exhaust gas pipe [Zaand the bypass conduit I4.

Fig. 2 illustrates an. example of the present invention wherein the gases from the auxiliary combustion chamber mix with the engine exhaust gases beforethey reach the gas turbine. Parts equivalent to those. of Fig, 1 are identified by the same numerals. As can be seen from the drawing, the auxiliary combustion chamber I5 is open at the bottom and. is in communication with the .to about 2500 F. The engine exhaust gases flow through an annular channel C surrounding the chamber I and mix with the gases therefrom, then pass to the turbine 2| and thenceto the atmosphere. The temperature of the gases in the exhaust gas pipe in varies with the load and speed of the engine, generally nearing about 1100 F. at full load in a four-cycle engine and less in a two-cycle engine. When the engine speed drops it consumes less air and more air flows through the bypass It which is heated, as mentioned above, to very high temperatures. Thus, when the much cooler exhaust gases are mixed with the gases from the combustion chamber l5, a rather high resultant temperature of from about 1000 to 1300 F. or even more results. The effect is that not only the air from the bypass is energized, but also that the engine exhaust is reheated before being expanded to near-atmospheric pressure, securing a greatly increased power production in the turbine 2i and consequently a higher supercharge pressure in the engine.

Fig. 3 shows an alternative embodiment of a supercharger suitable for an installation such as illustrated in Fig. 1. Here the bypass conduit id leads to a separate turbine 2m mounted on the same shaft as the blower l9 and the exhaust gas turbine 2 i If desired, the exhaust from the turbine 21a need not flow directly to the atmosphere but may be made to flow through a recuperative heat exchanger 28 interposed in an exhaust conduit 22a for the turbine 2 i a.

Pursuant to an ancillary feature of my invention, a starting motor 2-3 of any known kind e. g. electric is coupled to the supercharger sets by an overrunning clutch 2% which is adjusted to uncouple the motor 23 if the set begins to run faster than the starting motor. Where compressed air is available, the sets may also be started from a source 25 of compressed air or other gas which is connected by a pipe 25 with a control valve 2? to the nozzles of the turbine 25a (or what would be the same, to turbine 2 l The purpose of the above starting means is, according to my invention, to enable the supercharging sets to operate as a self-power-supporting gas turbine blower independently of the engine which maybe at standstill or running.

For starting, the sets are rotated by the meter 23 (or by compressed gas), with the valve it open to pass air to the conduit It, at a speed such that an air flow is set up through the blower 19, the intake pipe Ha, the bypass M, the combustion chamber i5, the turbine Zia, the exhaust conduit 22a, and the heat exchanger28 to the atmosphere. Now fuel is admitted to the combustion chamber 25 by opening the valve 28 and ignited. The hot gases reaching the turbine Qia begin to produce power and the sets speed up under its own power, uncoupling the clutch 24 when a certain speed is exceeded. With the engine that standstill all of the air is available for turbine 2 ta so that the sets quickly will attain a high speed. During this operation the turbine 2! is idle since no gases reach it from the engine. A high pressure is set up in the intake pipe Ma, and, if the engine it now is cranked for starting, a high supercharge pressure immediately is available.

This is of special importance for highly supercharged engines which, when started with intake 6 air of atmospheric pressure, do not produce high enough compression end temperatures to ensure reliable ignition for starting, particularly when the ambient air is very cold.

Such method of starting is of even greater importance for two-cycle engines which up to now had to use scavening pumps, either driven from the engine shaft or by an auxiliary power source. Two-cycle engines with exhaust turbine driven blowers of the known types cannot work satisfactorily at low loads or idling because the exhaust gas turbine when operating at the low temperatures prevailing under these conditions cannot provide suiiicient power even for scavenging.

My invention avoids all these complications by making the supercharging pressure independent of the working condition of the engine, and available even at engine standstill. All kinds of engines, including two-cycle engines of any type, can thus be successfully started and operated under all conditions with mechanically independent exhaust turbo-supercharger sets.

In installations where constant output at widely varying speeds is required, the present invention can be used to superimpose such characteristic on internal combustion engines, thus doing away with the mechanical, electric or hydraulic transmissions so far used for this purpose. If in an installation according to Figs. 1 and 3 on a locomotive to which a certain fuel quantity is fed, a higher torque is required, the engine speed drops and the air requirements of the engine drop in same proportion. With the position of control valve I6 unchanged, and speed of the supercharger set also practically unchanged for a second or so due to its inertia, more air will flow to the combustion chamber 15 in which correspondingly more fuel is burned so as to maintain the gas temperature at the entrance to the turbine Zia. This turbine, therefore, begins to supply extra power and, with proper design, the blower now is capable of supplying substantially the same air weight to the engine as before but at a higher pressure, enabling it to burn the same fuel quantity efiiciently at the reduced speed while supplying a higher torque in return. Naturally, a new higher equilibrium speed will be established for the supercharger set. This speed increase rises with the heating temperature in the chamber l5, the limit of which is fixed only by metallurgical considerations for the blade material used in the turbine 2la. With dropping torque requirements the reverse operation is effected by gradual closing of the control flap valve 16 and reduction of fuel feed to the combustion chamber IS.

The fuel consumed in the auxiliary combustion chamber of course has to be charged against the drive in the same manner as the losses incurred by electric or hydraulic transmission, for example on a locomotive. However, the drive according to my invention is superior to the present day transmission systems because extra fuel is consumed in the auxiliary combustion chamber only during the time when excess load or excess torque are actually furnished.

Fig. 4 shows an installation which preferably may be used in larger plants. Here the turbineblower set I 9, 2| is a normal supercharger set which will be referred to hereafter as a pressure charger, while a turbine 2H) drives a second blower I919 which discharges into the intake of the blower l9. This second set i912, Zib will be referred to hereinafter as a torque charger. 20b and 22b, respectively denote the intake and gas dischargeducts to blower 19b and. from the. turbine 2 l-Jb. The pressure chargeroperates continuously, while the torque charger. may be normally idling or operating at low load, and increasing its load only when required. to force the supercharging for overload or for high torque.

Since the speeds of both these sets are independent of each other, more. favorable working and regulating conditions for thetwo blowers result. The effectiveness of supercharging may be increased further by provision of air cooling means in the form of a cooling coil 3%] in the intake pipe wand another cooling coil 31 in the intake pipe H, respectively. In. this case starting is effected by the electric starting motor 23 coupled via the overrunning clutch 24to the torque charger. The pressure charger set may, during starting, be at a standstill, or be idling, and is started automatically the moment the engine starts.

Fig. 4 also shows diagrammatically a nonlimiting example of a control means for coordinating the operation of the engine with the pressure and torque chargers to. achieve plant operation characteristics which are desirable on locomotives and similar other drives. means to sense the engine speed, such as a flyball speed governor driven from the engine shaft by bevel gears 41. A governor lever 42 operates the fuel valve l3a for the engine by means of rods 43, 45 and a double armed lever 44 in the conventional manner. Avalve [3b permits limitation of the fuel supply by hand. The leve 42 further is connected by a rod 46 to a lever 41 whose left hand end is resiliently supported by a spring 48 and whose right hand end operates the flow control flapva-lve l6 through a crank C and rod 49. Means to sense the engine intake manifold pressure above a predetermined pressure is provided. Said means comprises an elastic bellows 58. The bellows is connected by a tube with the engine intake pipe H and presses down the left hand end of the lever 41 against the pressureof the spring 48 in the event the pressure in said engine intake pipe H exceeds a definite limit. A rod 52 with a screw and handwheel 53 permits hand adjustment of the fuel feed to the engine to be effected by moving the left hand end of the lever 44. A vapor pressure thermostat 54 is disposed in contact with the gases issuing from the combustion chamber I5. Said thermostat constitutes a means to sense the temperature of the hot gases leaving the burner, said means is connected by a tube 540. to an elastic bellows 55 which operates the fuel valve l8 by a crank 56. Ilia denotes a hand operated flap valve in the air intake to the combustion chamber and lBa denotes a hand operated fuel valve in the fuel intake line to said chamber. The thermostat 54 is adjusted in such a manner as to maintain a substantially constant high temperature of the gases flowing to the turbine 21b. The engine. ii! may be of any known type, for exam le a two-cycle compression-ignition engine.

The plant is started as follows: The motor 23 is energized. This causes the torque charger to rotate thereby setting up an air stream from the blower intake 2% through the torque charger blower 1%, the intake pipe 20, the pressure charger blower l9, the engine intake pipe Ila,

past the control flap valve l6 which is open to conduit 14, theopen valve 16a, the combustion chamber (to which fuel is not yet allowed to flow by keepingthe valve l8a closed), the torque charger turbine 2|}; and thence to the atmos- 40 denotes a.

phere,, at theturbine outlet. 22 Fuel is now torque charger turbine 21b increases fast caus ing the torque charger to speed up under its'own power and uncoupling the clutch 24. The motor can. now be deenergized. The torque charger quickly attains V an equilibrium speed when the turbine and blower powers balance. If the blower pressure rises too much, and possibly to prevent pumping (surging) of the torque charger blower I91), the pressure limiting bellows 50 comes into action by expanding and pressing the left hand side of the lever 41 down, thereby causing the control flap valve IE to throttle the air flow to the torque charger turbine 21?) thus reducing the speed of the torque charger.

The fuel valve 13a to the engine is set by operating, the handwheel 53 for starting, and the engineis cranked. Since the connection from the engine intake pipe Ila to the engine intake manifold II is never fully closed, the engine receives scavenging air from said manifold under pressure at the first moment and will start to operate. Exhaust gases now begin to flow through the engine exhaust pipe I2 to the pressure charger turbine 2| and the pressure charger set begins to operate. With increasing engine speed the lever 42 rises and gradually throttles the air flow to the bypass conduit [4 by moving the flap valve [6 counterclockwise, until at full speed only a slight flow of air is maintained through the combustion chamber [5 to keep a small flame burning. With reducing flow of combustion gases to the torque charger turbine 2E1) the speed of the torque charger will drop to a point where it is idling. In the meantime the pressure charger speed has increased, enabling it to supply the charging of the engine by itself. (While this method of regulating may be preferred for some cases, it is within the scope of this invention not to throttle the air flow to the bypass conduit completely thus keeping the torque charger always operating at reduced speed.)

With the fuel to the engine set by the valve I3b for a desired load, the pressure charger attains a certain speed and delivers (without or with the help of the torque charger) charging air of a certain pressure to the engine.

If now, due to increasing resistance, a higher torque is required, the lever 42 will begin to drop and normally would act to open the fuel valve l3a for admitting more fuel to the engine. The fuel quantity to the engine is, however, limited by the hand setting of valve 13b, so that the lever 42 will continue to drop, turning the lever 41 clockwise about its left hand end as a fixed point and admitting more air into the bypass conduit M by moving control flap valve I6 clockwise. Since the engine, due to its reduced speed, now takes less air, this does not cause a material decrease of pressure at lib and, on the contrary, as soon as a greater quantity of gases reaches the turbine 2), the torque charger speeds up and its blower |9b begins to operate as precompressor stage to the pressure charger blower 19 resulting in a higher charging pressure for the engine, increasing its mean effective pressure and consequently its torque. Due to the now higher air charge perworking stroka'the engine can burn the same fuel quantity at the lower speed as efficiently as it did at theformer higher speed, and by proper choice of pressures and speeds the 9 engine output can remain substantially unchanged, a characteristic most desirable for all kinds of vehicles and similar drives.

If the torque requirement decreases, the reverse motions take place and the engine speeds up with the power output remaining constant or approximately so. The cooling coil 30 may serve for cooling the air between the stage blowers [9b and I9, and, if desired, after cooling of the air charge to the engine may be achieved by the cooling coil 3 I.

It is immaterial for the purposes of my invention what particular type of engine is used. It may be of the compression-ignition or sparkignition type Working on two-cycle, four-cycle or dual cycle, single or multiple cylinder design.

It is also immaterial what types of machines are used for the supercharger means and whether or not cooling of the charging air is resorted to.

It is further immaterial for my invention what kind of fuel is burned in the engine and/or the auxiliary combustion chamber, and whether or not the same or different fuels are used in the engine and combustion chamber, respectively.

Having thus described the nature of my invention and in what manner the same is to be performed, I declare that what I claim is:

1. A combination with a reciprocating internal combustion compression-ignition engine having a turbine-driven blower set mechanically independent of the engine shaft and which set supplies compressed air to the engine: of a fuel burner externally of the engine and means for leading hot gases from said burner to said turbine, wherein there are provided means to sense the engine speed and means responsive to said sensing means to divert an increased portion of the air output of the turbine-driven blower to the burner as the engine speed falls to serve as combustion air therefor.

22. A combination with a reciprocating internal combustion compression-ignition engine having a turbine driven blower set mechanically independent of the engine shaft and which set supplies compressed air to the engine: of a controllable fuel burner externally of the engine and means for leading hot gases from said burner to said turbine, wherein conduit means and a bypass valve in said conduit means controlled by the engine speed is provided to divert a varying portion of the air output of the turbine-driven blower to the burner to serve as combustion air therefor, said valve being arranged to pass an increased quantity of air to the burner with falling engine speed, and wherein means is provided to increase the quantity of fuel with increasing quantity of bypassed air so that the speed of the set is increased with falling engine speed whereby engine intake manifold pressure increases with falling engine speed.

3. The combination with an internal combustion compression-ignition engine having a turbine driven blower set mechanically independent of the engine shaft which set supplies compressed air to the engine: of means connecting the air outlet of the blower of said set to the engine air intake pipe, means connecting the engine exhaust pipe with the inlet of the turbine of said set, a fuel burner externally of the engine, controllable bypass means to divert a portion of the air output of said blower to said burner to provide fresh combustion air therefor, means for leading hot gases from said burner to said turbine, means to sense the engine intake manifold pressure above a predetermined pressure, and means responsive to said sensing means to operate the controllable bypass means so as to reduce the quantity of air bypassed and thereby limit the degree of supercharging. 1

4. The combination with a reciprocating combustion compression-ignition engine having a turbine-driven blower set mechanically independent of the engine shaft: a second turbinedriven blower set mechanically independent of the engine shaft and of the first set, means to connect said blowers in series, means for connecting the outlet of the second blower in the series to the engine air intake pipe, a fuel burner externally of the engine, means to divert at least a portion of the air delivered to the engine air intake pipe to said burner to serve therein as combustion air, means for leading the hot gases from said burner to one of said turbines, and means directly connecting the engine exhaust pipe to the other turbine.

5. The combination with a reciprocating internal combustion compression-ignition engine having a turbine-driven blower set mechanically independent of the engine shaft: of means for connecting the outlet of the blower of said set to the engine air intake pipe, a controllable fuel burner externally of the engine, means to divert a portion of the air output of said blower to said burner to serve therein as combustion air, means for leading the hot gases from said burner to said turbine, means for connecting the engine exhaust pipe with the turbine of said set, means to sense the temperature of the hot gases leaving the burner, means responsive to said sensing means to vary the quantity of fuel fed to the burner so as to maintain the temperature of said hot gases substantially constant, means to sense the engine speed, and means responsive to the second sens ing means to increase the portion of the air diverted with falling engine speed so as to increase engine intake manifold pressure.

6. A combination with an internal combustion compression-ignition engine having regulatable means to feed fuel to it and supercharging blower means driven by exhaust gas turbine means, said blower and turbine means being mechanically independent of the engine shaft: of a fuel burner externally of the engine, regulatable means to feed fuel to the fuel burner, means to branch off a portion of the compressed air issuing from the blower means and lead it to the fuel burner, means for leading hot gases from the burner to the turbine means, and means simultaneously to control the fuel fed to the engine per working stroke, the air branched off from the blower means and the fuel fed to the burner.

7. The combination with an internal combustion compression-ignition engine having a turbine driven blower set mechanically independent of the engine shaft which set supplies compressed air to the engine: of means connecting the air outlet of the blower of said set to the engine air intake pipe, a fuel burner externally of the engine, means connecting the engine exhaust pipe with the inlet of the turbine of said set, means connecting the outlet of the burner to the inlet of the turbine, a controllable bypass means to divert a portion of the air output of said blower to said burner to provide fresh combustion air therefor, means to sense engine intake manifold pressure, means to sense the temperature of the hot gases issuing from the burner, and means responsive to said sensing means to control the quantity of air diverted to the burner and the amount of fuel bumainiemm n mannerasito i-Numfi r. m 1' m te engine intake manifold pressure at the degree of 2,318,905 Tljeyuppl M ay 11,1943

1 QQ FREDERICK NETTEL. -2,379-,4,55 A V r .1; 1; i: 5 i 23 L32 V-.-- v U v. U' EE#3,.-SE S... C ED v 7 21,442,669 "\S 2 l,.-J-- qE 9f The following references are of record in the 2,443,717 Birmann June 22,1948 file of this. w x ififirs UNITED PATENTS M Nubr 1 te 10 Number Country Date Y. e H 537,483 .Great Britain J.un 24,;1941 8 1 65 dqMul erwenv-w P 696,369 "Frarice 001;.14, 1930 2,280,765 Anxionnaz Apr. 21, 1942 

